1. Field of the Invention
The present invention relates to a signal reception apparatus and a method for communication systems, and more particularly, to a signal reception apparatus and a method for multi-band Ultra-Wideband communication systems capable of compensating for a channel attenuation difference among reception signals for respective bands occurring due to different central frequencies of respective bands.
2. Description of the Related Art
Ultra-Wideband communications known as wireless digital pulses are based on a wireless communication technology for transmitting large amounts of digital data through a wide range of frequency spectrum at a low power in a short range. The Ultra-Wideband communications can intermittently transmit data, using an ultra wideband comprising a few GHz to transmit wireless data, so that the Ultra-Wideband communications are expected to solve a frequency slot shortage phenomenon. Ultra-Wideband communications have an advantage that communications can be carried out at an ultra high-speed transmission rate of 500 Mbps-1 Gbps, but power consumption is low at a level of one one-hundredth of the power consumed for products such as cellular phones, wireless LANs, and the like, despite such a fast transmission speed. As the core technologies for the Ultra-Wideband communications, there are UWB modem technology of 100 Mps class, MAC technology for supporting the high QoS (Quality of Service), and small-sized antenna technology suitable to the wideband transmission.
In the meantime, single band and multi-band approaches have been proposed recently for the Ultra-Wideband communication technology standard. The single band approach is an approach which covers the entire bandwidth of an available frequency band, and the multi-band approach is an approach that uses plural sub-bands in which the entire bandwidth of an available frequency band is divided into the plural sub-bands. Current multi-band Ultra-Wideband communication systems use M sub-bands divided in the available frequency band existing between 3.1 GHz and 10.6 GHz.
FIG. 1 illustrates a frequency spectrum for a multi-band Ultra-Wideband communication system having sub-bands of M=16. Referring to FIG. 1, the first eight sub-bands (0-7) are allocated to a low frequency set, and the next eight sub-bands (8-15) are allocated for a high frequency set. In FIG. 1, a region marked Unexpected interferer denotes a region where interference can occur due to overlapping with a frequency band used in the other communication system. The following table shows central frequencies Fc, low band frequencies FL, and high band frequencies FH for respective sub-bands.
TABLE 1#A/BFcFLFH 0A3.523.2513.789 0B3.743.4714.009 1A3.963.6914.229 1B4.183.9114.449 2A4.44.1314.669 2B4.624.3514.889 3A4.844.5715.109 3B5.064.7915.329 4A5.285.0115.549 4B5.55.2315.769 5A5.725.4515.989 5B5.945.6716.209 6A6.165.8916.429 6B6.386.1116.649 7A6.66.3316.869 7B6.826.5517.089 8A7.046.7717.309 8B7.266.9917.529 9A7.487.2117.749 9B7.77.4317.96910A7.927.6518.18910B8.147.8718.40911A8.368.0918.62911B8.588.3118.84912A8.88.5319.06912B9.028.7519.28913A9.248.9719.50913B9.469.1919.72914A9.689.4119.94914B9.99.63110.16915A10.129.85110.389
For example, considering a frequency plan B as a reference, the sub-band 14B including the highest frequencies in the sub-band, has a central frequency of 9.9 GHz, and the sub-band 0B comprising the lowest frequencies in the sub-band has a central frequency of 3.74 GHz. When the two central frequencies are compared, it can be seen that the central frequency of sub-band 14B is 2.65 times the central frequency of sub-band 0B. Since signal attenuation in a channel is proportional to the square of the frequency, a signal transmitted through the 9.9 GHz band undergoes 7 times more channel attenuation (8.45 dB) as compared to a signal transmitted through a 3.74 GHz band.
FIG. 2 is a block diagram illustrating a signal reception apparatus for a conventional multi-band Ultra-Wideband communication system. Referring to FIG. 2, a signal reception apparatus for a conventional multi-band Wideband communication system has a multi-band index generation unit 10, a multi-band frequency generation unit 12, a multiplication unit 13, a correlation signal reception unit 14, and a signal processing unit 16.
The multi-band index generation unit 10 calculates a multi-band index m corresponding to each sub-band of a received multi-band Ultra-Wideband communication signal. The multi-band frequency generation unit 12 generates a multi-band frequency for each sub-band according to the multi-band index m inputted from the multi-band index generation unit 10. The multiplication unit 13 outputs a signal obtained by multiplying a multi-band Ultra-Wideband communication signal received through an antenna by a multi-band frequency. The correlation signal reception unit 14 outputs an integral value with respect to the signal of the multiplication unit 13 in regard to a certain integral time. Further, the signal processing unit 16 processes the signal outputted from the correlation signal reception unit 14 and restores a signal transmitted from a signal transmission apparatus.
However, when the correlation signal reception unit 14 processes a signal transmitted through each of M sub-bands, the signal reception apparatus for the conventional Ultra-Wideband communication system uses an approach to sum up energies of respective received signals over the time period with respect to respective sub-bands in regard to the same integral time. Accordingly, as described in relation to Table 1, the energy difference of a received signal per sub-band can occur up to 8.45 dB at maximum.
Such energy differences among received signals by sub-bands cause bit error rates (BERs) by sub-bands which are different from one another. At this time, an average bit error rate of the entire sub-bands is mainly affected by a bit error rate of a signal received through a sub-band having the largest channel attenuation, that is, a sub-band having the highest central frequency, which causes deterioration of the performance of the entire multi-band Ultra-Wideband communication system.